msm:rpm-log: add the mutex to protect read opertion

This commit will protect rpm log read operation. Then multithread
read the same rpm log buffer will not corruption.

CRs-Fixed: 646485
Change-Id: I0af7d8b3025d036cfa8927c2e37ef865075ff312
Signed-off-by: Pan Fang <fangpan@codeaurora.org>
posix_acl: handle NULL ACL in posix_acl_equiv_mode

Various filesystems don't bother checking for a NULL ACL in
posix_acl_equiv_mode, and thus can dereference a NULL pointer when it
gets passed one. This usually happens from the NFS server, as the ACL tools
never pass a NULL ACL, but instead of one representing the mode bits.

Instead of adding boilerplat to all filesystems put this check into one place,
which will allow us to remove the check from other filesystems as well later
on.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Ben Greear <greearb@candelatech.com>
Reported-by: Marco Munderloh <munderl@tnt.uni-hannover.de>,
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
mm/compaction: make isolate_freepages start at pageblock boundary